Impact of counterions on micelle formation and polymerization of 11-acryloyloxyundecyltrimethylammonium surfactants

Article abstract of DOI:10.1016/j.molliq.2020.113103

New surfactants based on the cationic monomer 11-acryloyloxyundecyltrimethylammonium with counterions bromide, nitrate, acetate, camphorsulfonate, 4-toluenesulfonate, trifluoroacetate were obtained in this work. In most cases counterions change the critical micelle concentration by 2–3 times (being compared with bromide) except sample with acetate counterions (in this case critical micelle concentration increases by an order of magnitude). Substitution of bromide for hydrophobic counterions (toluenesulfonate, trifluoroacetate, camphorsulfonate) does not lead to expected transformation of spherical micelles to long wormlike micelles. The polymerization of such monomers occurs according to the microemulsion mechanism involving micelles of monomers.

Full text of DOI:10.1016/j.molliq.2020.113103

Journal of Molecular Liquids 309 (2020) 113103
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Impact of counterions on micelle formation and polymerization of
11-acryloyloxyundecyltrimethylammonium surfactants
a
b
b
a
P.A. Fetin a, , I.M. Zorin , A.A. Lezov , V.I. Fetina , A. Yu Bilibin
⁎
a
Department of Macromolecular Chemistry, Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab, St. Petersburg 199034, Russia
Department of Molecular Biophysics and Polymer Physics, Physical Faculty St. Petersburg State University, 7/9 Universitetskaya nab, St. Petersburg 199034, Russia
b
a r t i c l e i n f o
a b s t r a c t
Article history:
New surfactants based on the cationic monomer 11-acryloyloxyundecyltrimethylammonium with counterions
bromide, nitrate, acetate, camphorsulfonate, 4-toluenesulfonate, trifluoroacetate were obtained in this work. In
most cases counterions change the critical micelle concentration by 2–3 times (being compared with bromide)
except sample with acetate counterions (in this case critical micelle concentration increases by an order of mag-
nitude). Substitution of bromide for hydrophobic counterions (toluenesulfonate, trifluoroacetate,
camphorsulfonate) does not lead to expected transformation of spherical micelles to long wormlike micelles.
The polymerization of such monomers occurs according to the microemulsion mechanism involving micelles
of monomers.
Received 16 January 2020
Received in revised form 22 March 2020
Accepted 6 April 2020
Available online 8 April 2020
Keywords:
Wormlike micelles
Surface-active monomers
Surfactant polymerization
Comb-like polyelectrolytes
© 2020 Elsevier B.V. All rights reserved.
1. Introduction
The use of cryogenic treatment allowed increasing the micelle life-
time. The gamma irradiation approach in this case has been success-
Self-organization of matter is the basis of most life processes [1]. The
amphiphilicity in most cases is the origin of the self-organization. Ionic
surfactants are the most common amphiphiles. Surfactants can be used
in absolutely different areas of human activity: it may be simple wash-
ing agents and something more complex composition, for example, sys-
tems for micelle catalyses applications [2,3] or components of drug
delivery systems [4]. Among all surfactants, a special attention should
be paid to surface-active monomers – surfactants acting as monomer
during polymerization processes [5]. Self-organized (usually micellar)
surfactant structures can be used to increase the polymerization rate
and obtain polymer products with a conversion close to 100%. Recently,
studies on kinetics of surfactants polymerization have been carried out
and it has been found that the Morgan-Kaler approach for
microemulsion polymerization can be used to identify the kinetic regu-
larities of such fast polymer syntheses. [6,7]. There are reports in the lit-
erature about the successful polymerization of micelles of monomers -
spherical [8], worm-like [9] and vesicular structures [10]. At first, one
of the goals of these works was to obtain polymeric copies of micelle
(so-called “polymerized micelles”) [11,12]. Unfortunately the time re-
quired for the formation of covalent bonds between surfactant mole-
cules during polymerization turns out to be comparable with the
lifetime of the micelle itself, and in some cases significantly more due
to the dynamic structure of the micelle. This phenomenon does not
allow the synthesis of exact polymer replicas of micelles of monomers.
ful used in the synthesis of true polymer copies of monomer micelles
[13]. The shape of self-organized structures of surfactants (spherical
and worm-like micelles) is influenced by the hydrophobicity of the
counterion [14]. Spherical-to-worm-like micelle transformation is
observed when hydrophobic counterions are added to a surfactant
solution. E.W. Kaler polymerized the worm-like micelles of
methacryloyloxyundecyltrimethylammonium bromide (the formation
of worm-like micelles was carried out by adding sodium tosylate)
[15]. The authors of this work observed anisotropy of micelle growth,
leading to polymer products with preservation of shape (the diameter
remained unchanged, the length increased several times). This phe-
nomenon was associated with the large lifetime of worm-like micelles
compared to spherical micelles. A similar phenomenon was discovered
during the polymerization of anionic worm-like micelles [9]. The
Walker and Kline group [16] investigated the polymerization of
cetyltrimethylammonium-4-vinylbenzoate (CTVB) worm-like micelles.
The water soluble polyelectrolyte-surfactant complex was a product of
this polymerization. The authors suggested that the chains of
polyvinylbenzoic acid (pVB) were solubilized with surfactant mole-
cules; lengths of the cylindrical aggregates were determined by the con-
tour length of the polymer chain. The polydispersity of the extracted
pVB acid were comparable to polymers obtained by free radical poly-
merization without micelle formation. It should be noted that there is
only a small number of works devoted to the study of the products of
such polymerization.
The aim of this work was to obtain a series of surface-active mono-
⁎
Corresponding author.
E-mail address: p.fetin@spbu.ru (P.A. Fetin).
mers
based
on
11-acryloyloxyundecyltrimethylammonium
https://doi.org/10.1016/j.molliq.2020.113103
0167-7322/© 2020 Elsevier B.V. All rights reserved.

2
P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
amphiphilic cation with various counterions and to study their self-
organization in water. Polymerization of such substances was not only
simple way of polymer syntheses, but also was considered as an inves-
tigation method for surfactant self-organizing solution. Two approaches
were used for pAUTA-X polyelectrolyte syntheses (Fig. 1). The first was
the polymerization of micelle forming monomers AUTA-X (the product
was called pAUTA-X (I)). The second was an ion exchange process per-
formed with pre-synthesized polyelectrolyte pAUTA-Br (I) (the prod-
ucts were referred as pAUTA-X(II)). Comparative analysis of pAUTA-X
(I) and pAUTA-X(II) series was under investigation.
(t, J = 6.7 Hz, 2H), 3.60–3.54 (m, 2H), 3.46 (s, 9H), 1.79–1.69 (m, 2H),
1.68–1.60 (m, 2H), 1.44–1.18 (m, 14H).
The synthesis of 11-methacryloyloxyundecyltrimethylammonium
bromide (MAUTA-Br), was carried out by
a similar method,
methacryloyl chloride was used instead of acryloyl chloride.
11-Acryloyloxyundecyltrimethylammonium nitrate (AUTA-NO3),
acetate (AUTA-Ac), trifluroacetate (AcF), toluene sulfonate (Ts),
camphorsulfonate (CS) was synthesized according to ion-exchange re-
action with silver salts (AgX) (Eq. (1)).
AUTA−Br þ AgX→AUTA−X þ AgBr
ð1Þ
2. Experiment
2.3. Synthesis of AUTA-X (an example is given for the synthesis of AUTA-Ts)
2.1. Materials
To a solution of silver nitrate (CAgNO3 = 0.6 M), a 20% excess NaOH
solution was added with stirring (CNaOH = 0.5 M); the precipitated
gray silver oxide powder was decanted and washed with water to a
neutral pH (washing was repeated at least three times). A stoichiomet-
ric amount of a p-toluenesulfonic acid solution (C = 1 M) was added to
the freshly prepared silver oxide with vigorous stirring until the precip-
itate dissolved. A stoichiometric amount of AUTA-Br solution (C =
0.4 M) was added to the resulting silver toluenesulfonate solution, and
the silver bromide precipitate was separated by centrifugation. The so-
lution was filtered through a 0.45 μm membrane filter, the product
was isolated by freeze drying and recrystallized from acetone-
methanol mixture. Dried to constant weight, AUTA-Ts structure was
confirmed by 1H NMR. AUTA-Ts yield after recrystallization 70%.
2,2′-Azobis(2-methylpropionamidine)dihydrochloride (AAPH) (Al-
drich), 11-bromoundecanol (Aldrich); NaOH (Vekton, Russia), AgNO3
(Vekton, Russia), acetic acid (Vekton, Russia), d(+)-Camphor-10-sul-
fonic acid (monohydrate) (Merck), 4-toluenesulfonic acid
(monohydrate) (Vekton, Russia) were used as received. Acryloyl chlo-
ride was distilled over CuCl at 73–74°С; methacryloyl chloride
(Sigma-Aldrich) was used as received; N-methylpyrrolidone (NMP)
was distilled over CaH2 at 125–128°С under reduced pressure
(0.12 bar) prior to use, trifluoroacetic acid was distilled under atmo-
sphere pressure at 72–73°С.
Deionized water (resistance not less than 12 MΩ) was used in all ex-
periments. Cellulose membrane tube with molecular weight cut-off
14000 (Sigma-Aldrich D9652) was used for dialysis.
2.4. Polymerization of AUTA-X
2.2. Synthetic procedures
The calculated amount of AUTA-X (C = 0.278 M) and AAPH (C =
1 g/l) was dissolved in water (4 ml) and placed in polypropylene reac-
tion vessel. Argon was bubbled through the solution for 15 min. The re-
action vessel was sealed with a conductometric sensor, and the vessel
was placed in a thermostat at 60 °C. After 1 h, the reaction mixture
was cooled and placed in a dialysis tube. Dialysis was performed against
water for 24 h (at least three water changes were used). The polymer
was isolated by freeze drying. The yields of the polymers after purifica-
tion and isolation were about 90%. The structure of the polymer was
11-Acryloyloxyundecyltrimethylammonium bromide (AUTA-Br)
was synthesized according to [17]. Briefly, 11-bromoundecanol reacted
with acryloyl chloride in NMP at −17 °C followed by reaction of ob-
tained 11-acryloyloxyundecylbromide with trimethylamine in acetoni-
trile. After solvent evaporation, the resulting AUTA-Br was purified by
crystallization from methanol-acetone mixture to give yield 74%.
1H NMR (400 MHz, CDCl3) δ, ppm: 6.37 (dd, J = 17.3, 1.5 Hz, 1H),
6.10 (dd, J = 17.3, 10.4 Hz, 1H), 5.80 (dd, J = 10.4, 1.5 Hz, 1H), 4.13
Fig. 1. The illustrative representation of synthetic routes for producing comb-like polyelectrolyte pAUTA-X in the work.

P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
3
confirmed by 1H NMR. Molecular weight of pAUTA-Br MsD = 80,000
was determined from the values of sedimentation constants s0 and
translational diffusion coefficients D0 in our previous work [17].
times τ). The dependence between 1/τ and the square of the scattering
4πn0
λ
Θ
2
vector q ¼
sinð Þ for all studied samples was a line passing
through the origin, indicating the diffusional character of the observed
processes (the experimental graphs can be found in supplementary ma-
terials) [21] (otherwise results were discarded). Translational diffusion
coefficient D was calculated from the slope of this line according to the
following relationship 1/τ = Dq2. Hydrodinamic radii were calculated
using Stokes-Einstein equation:
2.5. Br-exchange in pAUTA-Br polyelectrolyte [18]
The pAUTA-Br solution (100 mg, 3 ml) was placed in a dialysis tube.
Dialysis was performed against a 0.5 M solution of NaX (there X is es-
sential counterion, at least three NaX solution changes were used),
when the polymer solution was dialyzed against water and isolated by
freeze-drying. The completeness replacement of Br to Ts, CS, Ac coun-
terions was proved by 1H NMR data.
kT
D ¼
6πη0R
1H NMR spectra were recorded on a Bruker 400 MHz Avance spec-
trometer in CDCl3 and D2O. Conductivity measurements were per-
formed using an Expert-002 conductometer with a Mettler-Toledo
inLab 710 two-electrode immersion sensor (body - glass, electrodes -
platinum). For CMC measurements the external temperature-
controlled cuvette was used (25 °C). The CMC value was determined
as the cross point of the two straight lines in the plot of specific conduc-
tivity dependences from a surfactant concentration (the experimental
graphs can be found in supplementary materials).
Viscometric measurements were obtained on a Cannon-Ubbelohde
capillary viscometer at 25 °C in a 0.05 M aqueous NaCl or water. For
the calculation of the intrinsic viscosity [η] of polymer solutions the
Huggins equation [19] were used:
where ƞ0 - dynamic viscosity of solvent; D - translational diffusion coef-
ficient; R - hydrodynamic radius; k- Boltzmann constant; T - absolute
temperature;. All samples were centrifuged to remove dust before
investigation.
3. Discussions
The proposed method for the synthesis of AUTA-X by ion-exchange
reaction with silver salts allows obtaining the target compound without
column chromatography ion-exchange method. This synthesis
approach was successfully implemented for AUTA-X samples with
counterions: nitrate (NO3), trifluoroacetate (AcF), acetate (Ac),
toluenesulfonate (Ts), camphorsulfonate (CS). All AUTA-X substances
are soluble in chloroform, DMSO, water and aliphatic alcohols (metha-
nol, ethanol, butanol). The stoichiometry of such compounds was con-
firmed by 1H NMR spectroscopy. (Fig. 2A). There is an expanded
singlet at 4.01 ppm in the NMR spectrum of the AUTA-Ac, the singlet
is corresponded the presence of bound water in this compound. It was
proved by the addition of a few drops of H2O to the NMR-tube, after
this there aren't any new signals in the spectrum; the signal intensity in-
creased at 4.01 ppm. Based on the intensity of the signals in the AUTA-
Ac spectrum (Fig. 2B), we can assume the formation of AUTA-Ac × H2O
crystalline hydrate for this substance. The presence of bound water was
not detected by 1H NMR spectra for other AUTA-X compounds, (NMR
spectra can be found in supplementary materials) so no crystalline hy-
drate was formed. The tendency of AUTA-Ac to form crystalline hy-
drates is trained by the nature of the carboxyl group. It is known that
many acetate salts (for example sodium acetate) also form crystalline
hydrates [22].
ηsp
c
2
¼ ½ηꢀ þ Kh½ηꢀ c
where
η−η0
η0
ηsp - specific viscosity of solution, ηsp
;
c - polymer concentration, g/dl;
[η] - intrinsic viscosity, dl/g;
Kh - Huggins constant.
The luminescence spectra of a saturated pyrene aqueous solution
with the AUTA-X were recorded on a Shimadzu RF-5301 PC spectroflu-
orimeter. All solutions were aged for 3 days before measurements. For
CMC measurements the pyrene 1:3 ratio method was used. The pyrene
1:3 ratio plots have been approximated by a decreasing sigmoid of the
Boltzmann type, which is given by [20]
Two methods were used to determine the critical micelles concentra-
tions (CMC) of AUTA-X in water (spectrofluorimetry with a pyrene
probe [20], and conductometry method [23]). The CMC values for these
substances are presented in Table 1. Substitution of Br− to NO3− anion
slightly increases CMC value. This anions are well known anions in the
lyotropic (Hofmeister) series Ac− b H2PO4− b F− b Cl− b Br− b NO3− b PF6−.
In general, an increase of the hydrophilicity of the counterions leads to
higher values of CMC. According to Hofmeister series, AUTA-Br should
have lager CMC values. CMC of AUTA-NO3 deviates from this assumption,
but the sample AUTA-Ac are in good correlation with Hofmeister series.
AUTA-Ac has an order of magnitude greater CMC value than the original
AUTA-Br. (Fig. 3A, B, Table 1). The CMC value of AUTA-AcF is lower than
that of AUTA-Ac due to the higher hydrophobicity of trifluoroacetate
counterion. Similar effect was observed for dimeric cationic surfactant
ethanediyl-bis-(dimethyltetradecylammonium) with counterions Br−
(CMC = 0.14 mM) NO−3 (CMC = 0.14 mM), Ac− (CMC = 0.61 mM),
AcF− (CMC = 0.14 mM) [24]. The CMC value of AUTA-CS is higher
than AUTA-Ts due to large steric effects of camphorsulfonate anion.
The viscosity of a surfactant solution is extremely sensitive to any
changes in the shape of the particles. Therefore, differences in the spe-
cific viscosity (ƞsp = (t-t0)/t0) values of AUTA-X solutions served as a
criterion indicating changes in the shape of AUTA-X micelles. For the
compounds under investigation, no kinks were found in the concentra-
tion dependence of the specific viscosity of surfactant solutions above
I1
I3
A2−A1
ꢀ
ꢁ
¼
þ A2
C−C0
ΔC
1 þ exp
where
I1/I3 - intensity ratio in the luminescence pyrene spectrum at wave-
lengths I1 = 273 nm I3 = 283 nm;
A1 and A2 - upper and lower bounds of I1/I3;
C - surfactant concentration, M;
C0 and ΔC - approximation parameters.
The CMC value was determined as CMC = C0 + 2ΔC. This CMC value
is correspond the interception of the rapidly varying part and the nearly
horizontal part at high concentration of the pyrene 1:3 ratio plots (The
pyrene 1:3 ratio plots can be found in supplementary materials).
DLS measurements were performed with PhotoCor Complex
(Photocor Instruments Inc., Russia) instrument equipped with real-
time correlator (288 channels, 10 ns) in scattering angle range
30–140° at 25
0.1 °C, with laser light source having wavelength,
λ = 405 nm. Autocorrelation functions of scattered light intensity was
processed using DynaLS software (providing the distributions of
scattered light intensity and, therefore, distributions of relaxation

4
P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
Fig. 2. 1H NMR spectrum of AUTA-Ts (spectrum A) and AUTA-Ac × 1H2O (spectrum B) in CDCl3.

P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
5
Table 1
(Fig. 4A). No differences were found between the specific viscosity of
the solutions of AUTA-Ts and AUTA-Br with a stoichiometric amount
of sodium toluenesulfonate (blue squares and open red squares in
Fig. 4A). At that time, the dependence of the specific viscosity of the
MAUTA-Br with the stoichiometric amount of sodium toluenesulfonate
on the surfactant concentration has a piecewise broken form and begins
to increase sharply at a surfactant concentration greater than 0.192 M
(The concentration was called CMC 2). This viscosity dependence is
characteristic of a solution containing worm-like micelles. It is worth
noting that it was not possible to use MAUTA-Ts obtained by ion-
exchange reaction with silver toluenesulfonate (without impurities of
foreign salts). The MAUTA-Ts isolated from water solution by freeze
drying has limited solubility in water.
Dependence of the CMC of AUTA-X in water 25 °C, and the specific viscosity (ƞsp) of the
solution of these surfactants at a surfactant concentration equal to 0.35 M (16 × CMC
(AUTA-Br)).
Surfactant
CMC, М
ƞsp = (t-t0)t0
AUTA-Br
AUTA-NO3
AUTA-AcF
AUTA-Ac
AUTA-Ts
AUTA-СS
0.012a; 0.014b
0.015a; 0.023b
0.032a; 0.041b
0.148a; 0.26b
0.009a; 0.015b
0.063a; 0.033b
0.49
0.50
0.81
0.81
1.16
0.84
a
CMC is determined by spectrofluorimetry with a pyrene label [20].
CMC is determined by conductometry [23].
b
DLS technique was used for detailed study of the characteristics of
surfactants aggregates in solution (Table 2). Only small particles with
a hydrodynamic radius of 0.7 and 0.8 nm were obtained in a solution
of AUTA-Br and MAUTA-Br at concentrations of 0.272 M (16 × KKM
AUTA-Br). Those values virtually corresponds to the radius of spherical
micelles of surfactants in which the AUTA-Br and MAUTA-Br molecules
are present in the loop conformation, as indicated in a several studies
[25,26]. At the same concentration of AUTA-Ts and MAUTA-Br in solu-
tion containing sodium toluenesulfonate (TsONa), relatively large parti-
cles with a hydrodynamic radius 2.7 and 6.2 nm were observed. The
value of hydrodynamic radius of MAUTA-Br + TsONa is much higher
than the length of this molecule in fully stretched conformation. The au-
thors of [15] were observed the worm like micelles in the solution of
MAUTA-Br by cryo-TEM. In our case overvalued hydrodynamic radius
CMC. To identify differences in the shape of micelles, the specific viscos-
ity of surfactant solutions was determined and compared at a concen-
tration of 0.35 M. This concentration is higher than the critical
concentration of AUTA-Ac micelle formation (The surfactant with
highest CMC value of AUTA-X series, Table 1).
The specific viscosity of samples with toluenesulfonate counterion
AUTA-Ts is about 2.4 times higher than the viscosity of AUTA-Br sam-
ples and also is higher than the viscosity of other AUTA-X. Nevertheless,
this value of specific viscosity is not typical for a solution containing
worm-like micelles. We compared the specific viscosities of the AUTA-
Ts derivatives solutions with the MAUTA-Br solution viscosity, where
the authors [15] observed the formation of worm-like micelles with
the addition of stoichiometric amounts of sodium toluenesulfonate
Fig. 3. Dependence of (I1/I3) intensity ratio of pyrene luminescence at wavelengths λ1 = 373 nm and λ3 = 383 nm (A), and the electrical conductivity of AUTA-Ac solution (B) from the
concentration of AUTA-Ac.
Fig. 4. Dependences of the specific viscosity ηsp = (t-t0)/t0 on the surfactant concentration: A: mixture MAUTA-Br and TsONa (1:1), mixture AUTA-Br and TsONa (1:1), AUTA-Ts. B:
AUTA-Br, MAUTA-Br. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

6
P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
Table 2
Parameters of self-organized structures AUTA-Tc and MAUTA-Br with sodium toluenesulfonate (1:1) in water obtained from data of dynamic light scattering.
Surfactant
C = 16 × CMC (AUTA-Br)
D × 107 cm2/c
Rh, nm
C = 5 × CMC (AUTA-Br)
L1.6, nm
L3.2, nm
D × 107 cm2/c
Rh, nm
L1.6, nm
L3.2, nm
AUTA-Br
MAUTA-Br
AUTA-Ts
MAUTA-Br + TsONa
29.5
33.4
9.1
0.06
0.08
0.2
0.04
0.8
0.7
2.7
6.2
–
–
13
45
–
–
7
35
–
–
11.5
11.5
–
–
2.1
2.1
–
–
9
9
–
–
5
5
0.04
0.06
3.96
values of MAUTA + TsONa may corresponds to the presence of the
worm like micelles in studied solution. To estimate the hydrodynamic
parameters of micelles the model of a translation diffusion of rigid rod
[27] was used:
(5 × CMC (AUTA-Br)) leads to rod-like particles with a contour length
comparable with that of AUTA-Ts. These results are in good correlation
with the data of viscometry of the surfactant solutions (Fig. 4A). Similar
contour length (L = 40 nm) of worm-like micelles was found for
MAUTA-Br (transformation was induced by TsONa addition) by small
angle neutron scattering [15].
The difference in the contour length of the worm-like micelles may
be due to the significant polarity of the ester acrylic group in the
AUTA-Ts molecule (Fig. 1). This statement can be qualitatively demon-
strated using the packing parameter (Ns) of the surfactant molecule pro-
posed by Israelachvili (Eq. (3)).
"
#
ꢀ ꢁ
ꢀ ꢁ
ꢀ ꢁ
−1
−2
kT
3πη0L
L
d
L
d
L
d
D ¼
ꢁ
ln
þ 0:312 þ 0:566
−0:100
ð2Þ
where L – micelle contour length; d – hydrodynamic diameter of rod-
like object. The boundaries of hydrodynamic diameter values d may
be estimated from the length of fully stretched and looped MAUTA-Br
molecule and corresponds to the values 3.2 nm and 1.6 nm.
v
To estimate the contour length (L) of micelles, Eq. (2) was solved
graphically (Fig. 5) using the two possible diameter of cylinder (d)
equal to 1.6 nm or 3.2 nm. The first value (d = 1.6 nm) corresponds
to the loop conformation of surfactant molecule and equals to diameter
of the AUTA-Br spherical micelle in solution. The second values corre-
spond to fully extended conformation of surfactant molecules The esti-
mation showed that the solution of MAUTA-Br + TsONa (1:1) contains
rod-like objects with a contour length of 33–46 nm (Fig. 5). The same
estimation was done for AUTA-Ts diffusion coefficients. AUTA-Ts solu-
tions contains particles with a shorter contour length (7–13 nm)
(Table 2.). A decrease in the concentration of MAUTA-Br to 0.085 M
Ns ¼
ð3Þ
a0 ꢁ Lc
where
v - the volume of the hydrophobic part of the surfactant molecule;
а0 - surfactant polar group area;
Lc - the length of the hydrophobic part of the surfactant [28].
For the formation of worm-like micelles, the packing parameter
should be in range from 1/3 to 1/2, below 1/3 only spherical micelles
Fig. 5. Dependence of translation diffusion coefficients D on contour length L of MAUTA-Br + TsONa, obtained by Eq. (2) for d = 1.6 nm (continuous line) for d = 3.2 nm (dashed line), and
by Stokes-Einstein model where L = d = R (dotted line). A horizontal bold line corresponds to the diffusion coefficients obtained by DLS (see Table 2). Vertical lines are projections of
intersections of theoretical curves and experimental horizontal lines, which corresponds to graphical solutions of Eq. (2) and Stokes-Einstein.

P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
7
Table 3
are formed. The introduction of a hydrophobic counterion increases the
volume of the hydrophobic part (v) of the surfactant molecule, leaving
the length of the hydrophobic part (Lc) of the surfactant almost un-
changed due to solubilization of counterion. Therefore, when the
anion bromide (Br) is replaced to the counterion of toluene sulfonate
(Ts) in the MAUTA-Br molecule, the numerator in Eq. (3) increases
with the denominator unchanged. This leads to an increase in the pack-
ing parameter (Ns) and the formation of long worm-like micelles in so-
lution becomes preferable. Due to the presence of a polar group (acrylic
acid ester) in the AUTA-Ts molecule, an increase in the numerator
(3) becomes insufficient to increase the packing parameter (Ns) due to
the large values in the denominator. Therefore, only worm-like micelles
of small length are formed in the solution.
Values of intrinsic viscosity [η] and Huggins constants Kh of solutions of comb-like poly-
electrolytes in 0.05 M aqueous NaCl, hydrodynamic radii (R1h, Rh2 correspond fast and slow
modes in size distribution): pAUTA-Х(I) from polymerization of AUTA-X in water (СAUTA-
Х = 0.272 М); pAUTA-Х(II), from ion exchange on pAUTA-Br polyelectrolyte.
Counter
ions: X
pAUTA-Х(I)
pAUTA-Х(II)
[η], dl/g
0.01
Kh
Rh1; R2h, nm
С = 0.7 g/dl
[η], dl/g
0.01
Kh
Rh1; R2h, nm
С = 0.7 g/dl
Br−
1.50
1.53
0.80
1.18
0.64
0.78
0.05 9; 40
0.04 9; 34
0.78 6; 22
0.04 6; 23
0.72 5; 17
0.37 6; 20
1.50
1.51
1.50
1.10
0.73
0.87
0.05 9; 40
0.04 8; 43
0.21 7; 35
0.05 6; 22
0.66 7; 30
0.20 6; 22
NO−3
Ас−
AcF−
Ts−
CS−
Analysis of the products of the AUTA-X polymerization served as an
additional way of studying the nature of self-organized structures in so-
lution. The polymerization of AUTA-X was carried out at a surfactant
concentration equal to 0.272 M, which was 16 times higher than the
critical micelle concentration for AUTA-Br. The polymerization process
was monitored by the change in the electrical conductivity of the mono-
mer solution (Fig. 6A, B). The plots of time dependences of electrical
conductivity during polymerization have a topology characteristic of
polymerization of monomers complicated by micellization [29]. A
sharp increase in electrical conductivity at the initial stage (the first
5 min) was observed due to the heating of the reaction mixture (from
20 °C to 60 °C). The next abrupt decrease in electrical conductivity
was caused by the transformation of the charge carriers from mono-
meric to polymer (the next 5 min of polymerization). The mobility of
the charge carriers decreases, and their number also decreases during
polymerization due to the greater condensation of counterions on the
polymer chain, compared with the degree of counterion bonding with
monomer micelles. Monomer conversion data (Fig. 6A) were found to
confirm the proposed scheme of the polymerization process within
10 min of synthesis. It should be noted that for more hydrophobic coun-
terions (Ts, CS), the maximal conductivity of the monomer solution at
60 °C is lower than for the monomer with counterions (Br, NO3),
which is associated with lower mobilities of these counterions, as well
as with their greater degree of bonding with monomer micelles due to
solubilization by micelles of AUTA-X. The change in electrical conductiv-
ity during the polymerization of AUTA (Ts, CS) is also lower compared to
other monomers (Fig. 6B).
hydrophobic counterions (Table 3). This can be caused by a greater
compaction of the polymer coil due to a complex of hydrophophobic
and ionic interactions between counterions and the polymer chain.
To assess the effect of the nature of the counterion on the degree of
polymerization of pAUTA-X, polymeric objects pAUTA-X were synthe-
sized using ion exchange on a pre-synthesized pAUTA-Br polyelectro-
lyte. In the further text these objects were named pAUTA(II) to
distinguish them from polymers obtained by polymerization of AUTA-
X (named pAUTA-X(I)). Polymers formed by ion exchange on a pre-
synthesized pAUTA-Br polyelectrolyte (pAUTA(II)) have an equal de-
gree of polymerization; therefore, they can be a reference standard for
assessing the deviation of pAUTA-X (I) degree of polymerization. The
values of the intrinsic viscosity for pAUTA-X (I) and (II) are close and
are in good correlation with each other (Table 3). The difference is ob-
served only for pAUTA-Ac (I) (Table 3). This effect may be associated
with abnormally high values of the critical micelle concentration for
AUTA-Ac (Table 1). The concentration of AUTA-Ac during polymeriza-
tion is comparable with the CMC value for this surfactant. There is a sig-
nificant fraction of the monomer unassociated into micelles, which
most likely causes a decrease in the characteristic viscosity of pAUTA-
Ac (I) in comparison with pAUTA-Ac(II). Upon dissolution of both
PAUTA-X (I) and PAUTA-X (II) polymers, the formation of stable aggre-
gates is observed by dynamic light scattering (Table 3, Fig. 7). The hy-
drodynamic radii and size distribution of pAUTA-X (I) and (II) are
close to each other; all polymers samples demonstrate bimodal size dis-
tribution in solution. There are same difference in R2h between polyelec-
trolyte pAUTA-Ac,Ts (I) and (II). (Distributions of scattering light
intensity (I/Imax) at 90° on the hydrodynamic radii can be found in the
supplementary). We assume that one of the main driving forces of ag-
gregate formation is hydrophobic interaction of aliphatic tails of
To study the effect of the counterion nature on the molecular weight
of the pAUTA-X polyelectrolytes, the viscometric method was used; the
viscosity of the solutions was measured in 0.05 M aqueous NaCl. As ex-
pected, the intrinsic viscosity [η] of solutions decreases with the transi-
tion from samples with polar counterions to samples with more
Fig. 6. Dependence of the electrical conductivity of the AUTA-X (σ) solution on the polymerization time. (CAUTA-X = 0.272 M, 60 °C, Ci = 1 g/l, initiator 2,2′-azo-bis-2-amidinopropane
hydrochloride). A: polymerization of AUTA-Br (q – monomer conversion by NMR); B: polymerization of AUTA-X (X = Ts (1), CS (2), AcF (3), NO3 (4), Ac (5)).

8
P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
Fig. 7. Distributions of scattering light intensity (I/Imax) at 90° on the hydrodynamic radii (Rh) for monomer AUTA-Br (A), AUTA-Ts (solid lines) and polymers (dote lines).
comb-like polyelectrolyte, the observed Huggins constants for pAUTA-
Ac(I) and pAUTA-Ts (I) is higher than samples formed by ion exchange
(pAUTA-Ac, Ts(II)). Decreasing solvent quality for pAUTA-Ac,Ts (I) can
be assumed in comparison of pAUTA-Ac,Ts (II). Features of the aggre-
gates formed from pAUTA-Br were reported in our recent work [18].
Ion exchange of Br− to hydrophobic Ts− anion increases amount of ag-
gregate fraction.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.molliq.2020.113103.
References
[1] J.M. Lehn, Towards complex matter: Supramolecular chemistry and self-
organization, Eur. Rev. 17 (2009) 263–280, https://doi.org/10.1017/
S1062798709000805.
4. Conclusion
[2] F. Rahman, M.Z.A. Rafiquee, Influence of polyethylene glycol and surfactant mixed
system on the rate of alkaline hydrolysis of benzocaine, J. Mol. Liq. 291 (2019)
https://doi.org/10.1016/j.molliq.2019.111262.
[3] E.J. Fendler, J.H. Fendler, Micellar catalysis in organic reactions: kinetic and mecha-
nistic implications, Adv. Phys. Org. Chem. 8 (1970) 271–406, https://doi.org/10.
1016/S0065-3160(08)60323-8.
[4] J.O. Kim, A.V. Kabanov, T.K. Bronich, Polymer micelles with cross-linked polyanion
core for delivery of a cationic drug doxorubicin, J. Control. Release 138 (2009)
197–204, https://doi.org/10.1016/j.jconrel.2009.04.019.
[5] H.-P. Hentze, E.W. Kaler, Polymerization of and within self-organized media, Curr.
Opin. Colloid Interface Sci. 8 (2003) 164–178, https://doi.org/10.1016/S1359-0294.
[6] I.M. Zorin, E.P. Podolskaya, A.Y. Bilibin, On the kinetics of micellar polymerization.
Acryloylaminoalkanoates case study, Eur. Polym. J. 110 (2019) 355–363, https://
doi.org/10.1016/j.eurpolymj.2018.11.045.
New surfactants based on the amphiphilic cation 11-
acryloyloxyundecyltrimethylammmonium with counterions nitrate,
acetate, trifluoroacetate, 4-toluenesulfonate, camphorsulfonate were
obtained. It was shown that for these surfactants, a change in the hydro-
phobicity of the counterion does not lead to the expected transforma-
tion of spherical micelles into long worm-like micelles, only short
cylindrical micelles can be formed. The CMC of the derivative with ace-
tate counterion AUTA-Ac is an order of magnitude greater than the
values of CMC of surfactants with the other counterions. The polymeri-
zation of the resulting compounds is influenced by micelle formation.
With the exception of the derivative with an acetate counterion, the de-
gree of polymerization of the polymers does not depend on the nature
of the counterion.
[7] I.M. Zorin, T.M. Shcherbinina, E.I. Demidov, E.V. Mechtaeva, N.A. Zorina, P.A. Fetin,
A.Y. Bilibin, Polyelectrolyte-colloid complex formation via polymerization: reaction
kinetics in direct micelles, inverted micelles, and homogeneous solution studied
by NMR and conductometry, Colloid Polym. Sci. 297 (2019) 1169–1176, https://
doi.org/10.1007/s00396-019-04531-4.
[8] K. Chatjaroenporn, R.W. Baker, P.A. FitzGerald, G.G. Warr, Structure changes in mi-
celles and adsorbed layers during surfactant polymerization, J. Colloid Interface
Sci. 336 (2009) 449–454, https://doi.org/10.1016/j.jcis.2009.04.059.
[9] Z. Zhu, Y.I. Gonz??lez, H. Xu, E.W. Kaler, S. Liu, Polymerization of anionic wormlike
micelles, Langmuir 22 (2006) 949–955, https://doi.org/10.1021/la052384i.
[10] S. Liu, D.F. O’Brien, Stable polymeric nanoballoons: Lyophilization and rehydration
of cross-linked liposomes, J. Am. Chem. Soc. 124 (2002) 6037–6042, https://doi.
org/10.1021/ja0123507.
CRediT authorship contribution statement
P.A. Fetin: Writing - review & editing, Investigation, Funding acqui-
sition. I.M. Zorin: Methodology, Writing - review & editing. A.A. Lezov:
Investigation, Conceptualization, Writing - review & editing. V.I. Fetina:
Investigation. A. Yu Bilibin: Validation.
[11] D. Cochin, F. Candau, R. Zana, Photopolymerization of micelle-forming monomers. 1.
Characterization of the systems before and after polymerization, Macromolecules 26
(1993) 5755–5764, https://doi.org/10.1021/ma00073a033.
Declaration of competing interest
[12] S. Hamid, D. Sherrington, Polymerized micelles: fact or fancy? J. Chem. Soc. Chem.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Commun. (1986) 936–938.
[13] X. Zhang, M. Wang, T. Wu, S. Jiang, Z. Wang, In situ gamma ray-initiated polymeri-
zation to stabilize surface micelles, J. Am. Chem. Soc. 126 (2004) 6572–6573,
https://doi.org/10.1021/ja049431y.
[14] L.J. Magid, The surfactant - polyelectrolyte analogy, J. Phys. Chem. B 102 (1998)
4064–4074, https://doi.org/10.1021/jp9730961.
[15] S. Liu, Y.I. Gonzalez, D. Danino, E.W. Kaler, Polymerization of wormlike micelles in-
duced by hydrotropic salt, Macromolecules 38 (2005) 2482–2491, https://doi.org/
10.1021/ma047646m.
[16] M.J. Gerber, S.R. Kline, L.M. Walker, Characterization of rodlike aggregates generated
from a cationic surfactant and a polymerizable counterion, Langmuir 20 (2004)
8510–8516, https://doi.org/10.1021/la048929a.
Acknowledgements
The work was supported by research park of St. Petersburg Univer-
sity: RC of Magnetic resonance, Chemistry Educational Centre.
Fetin P.A. and Fetina V.I. are grateful to RSF Grants № 19-73-00059.
[17] N.V. Tsvetkov, P.A. Fetin, A.A. Lezov, A.S. Gubarev, L.I. Achmadeeva, A.A. Lezova, I.M.
Zorin, A.Y. Bilibin, Colloid solution of surfactant monomers and polyelectrolyte: po-
lymerization and properties of the resulting interpolyelectrolyte complexes, J. Mol.
Liq. 211 (2015) 239–246.
[18] P.A. Fetin, I.M. Zorin, E.V. Mechtaeva, D.A. Voeiko, N.A. Zorina, D.A. Gavrilova, A.Y.
Bilibin, Formation of the structure of interpolyelectrolyte complex in solid state:
Data availability
Raw experimental data are available on request or in the
supplementary.

P.A. Fetin et al. / Journal of Molecular Liquids 309 (2020) 113103
9
role of comb-like amphiphilic polyelectrolyte, Eur. Polym. J. 116 (2019) 562–569,
https://doi.org/10.1016/j.eurpolymj.2019.04.052.
[19] M.L. Huggins, The viscosity of dilute solutions of long-chain molecules. IV. Depen-
dence on concentration, J. Am. Chem. Soc. 64 (1942) 2716–2718, https://doi.org/
10.1021/ja01263a056.
[20] J. Aguiar, P. Carpena, C.C. Ruiz, On the determination of the critical micelle concen-
tration by the pyrene 1:3 ratio method, J. Colloid Interface Sci. 258 (2003)
116–122, https://doi.org/10.1016/S0021-9797(02)00082-6.
[24] S. Manet, Y. Karpichev, D. Bassani, R. Kiagus-Ahmad, R. Oda, Counteranion effect on
micellization of cationic gemini surfactants 14-2-14: Hofmeister and other counter-
ions, Langmuir 26 (2010) 10645–10656, https://doi.org/10.1021/la1008768.
[25] S.M. Hamid, D.C. Sherrington, Novel quaternary ammonium amphiphilic (meth)ac-
rylates: 1. Synthesis, melting and interfacial behaviour, Polymer (Guildf) 28 (1987)
325–331, https://doi.org/10.1016/0032-3861(87)90426-5.
[26] T. Friedrich, B. Tieke, F.J. Stadler, C. Bailly, Improvement of elasticity and strength of
poly(N-isopropylacrylamide) hydrogels upon copolymerization with cationic
surfmers, Soft Matter 7 (2011) 6590, https://doi.org/10.1039/c1sm05777d.
[27] J.G. De La Torre, M.C.L. Martinez, M.M. Tirado, Dimensions of short, rodlike macromol-
ecules from translational and rotational diffusion coefficients. Study of the gramicidin
dimer, Biopolymers 23 (1984) 611–615, https://doi.org/10.1002/bip.360230402.
[28] J.N. Israelachvili, Intermolecular and Surface Forces, 2nd ed. Academic Press, 1992.
[29] A.Y. Bilibin, T.M. Shcherbinina, Y.A. Kondratenko, N.A. Zorina, I.M. Zorin, Micellar po-
lymerization of alkylammonium 2-acrylamido-2-methylpropane sulfonates in the
solvents of different polarities and properties of resulting polyelectrolyte-
surfactant complexes, Colloid Polym. Sci. 293 (2015) 1215–1225, https://doi.org/
10.1007/s00396-015-3497-8.
[21] H.Z. Cummins, Photon-correlation and Light-beating Spectroscopy, Plenum Pre,
New York, 1974.
[22] T. Wada, Y. Matsuo, Studies on salt hydrates for latent heat storage: Vi. Preheating
effect on crystallization of sodium acetate trihydrate from aqueous solution with a
small amount of disodium hydrogenphosphate, Bull. Chem. Soc. Jpn. 57 (1984)
561–563, https://doi.org/10.1246/bcsj.57.561.
[23] A. Domínguez, A. Fernández, N. Gonzalez, E. Iglesias, L. Montenegro, Determi-
nation of critical micelle concentration of some surfactants by three tech-
niques, J. Chem. Educ. 74 (1997) 1227–1231, https://doi.org/10.1021/
ed074p1227.